GdkColor is about to be deprecated, so move to GdkRGBA instead.
It might be worth considering using cairo patterns for the gradients
rather than using custom code to render gradients to a pixbuf which
is then drawn with cairo, but for now this is just a straight port
of the existing code.
https://bugzilla.gnome.org/show_bug.cgi?id=650586
If mutter is going to be a "real" library, then it should install its
includes so that users can do
#include <meta/display.h>
rather than
#include <display.h>
So rename the includedir accordingly, move src/include to src/meta,
and fix up all internal references.
There were a handful of header files in src/include that were not
installed; this appears to have been part of a plan to keep core/,
ui/, and compositor/ from looking at each others' private includes,
but that wasn't really working anyway. So move all non-installed
headers back into core/ or ui/.
https://bugzilla.gnome.org/show_bug.cgi?id=643959
